Unclenick, great graphics.
Tell that story and run the pictures backwards and it's almost exactly what happens when the round fires. Case body expands, sucks neck brass back into the body part, shrinks back down after pressure drops and bullet exits. Result is a fatter case with a bit more case headspace and a shorter neck. The case is now shorter from head to mouth than before it was fired.
Such are the life cycles of a new brass case from shooting, resizing reloading, reshooting, resizing, reloading, reshooting resizing. . . . . . .
After each cycle for a given shot, the case overall length grows a thousandth or so.
US Navy Distinguished Marksman Badge 153
Former US Navy & Palma Rifle Team Member
NRA High Power Master & Long Range High Master
NRA Smallbore Prone Master